1. Field of the Invention
The present invention generally relates to optical viewing devices, and more particularly to a device which is used to inspect the end faces of cleaved optical fibers.
2. Description of the Prior Art
The use of optical fibers for high speed communication and data transmission via optical signals has become well established. It is often necessary to splice an intermediate portion of optical fiber, due to breakage of the fiber, or to connect a terminal end of a fiber to another fiber in order to reach very distant locations. The condition of the fiber end face is important since irregularities in the surface of the end face may result in higher signal loss across the splice. With some optical connectors, such as biconic and ferrule connectors, the condition of the end faces may be inconsequential, since the end faces are typically (but not always) smoothed in a polishing operation. See, e.g., U.S. Pat. No. 3,902,784 issued to Dakss et al. For mechanical and fusion splices, however, a cleaving operation can often produce a smooth end face without the complicated polishing step. Moreover, it would be more difficult to polish the end faces of fibers which are to be connected via a mechanical or fusion splice, since there is no structure inherent in such splices (like a ferrule) which serves to hold the terminal end of the fiber.
In the cleaving operation, which typically requires special cleaving devices having strict mechanical tolerances, a score line is produced along the outer surface of a fiber, and the fiber is then bent or pulled over a form, causing it to break at the score line. Unfortunately, these devices do not always provide a perfect cleave, i.e., the end faces may possess unacceptable defects such as irregular cracks, lips, or shattered ends, and the operation must be repeated. The operation is further complicated by the fact that the fibers must be removed from the cleaver and placed in another device before the end faces of the fibers can be inspected. For example, U.S. Pat. No. 4,671,629 depicts a device which is used to examine the surface finish of fiber optic ends. This device is rather cumbersome in that it requires access to both ends of the optical fiber. Alternatively, a pocket-type microscope, such as the one sold by FOTEC of Japan under model number V100, may be used to view the fibers. That device includes a light attachment which swivels away from the main microscope body to illuminate the object viewed from an angle, but the microscope uses plastic lenses which have poor optical properties, and is not well-suited for inspecting bare fibers. Finally, expensive interferometers may be used to inspect the end faces. All of the prior art devices, however, still require removal of the fibers from the cleaver prior to inspection. It would, therefore, be desirable and advantageous to devise an instrument for visually inspecting the end face of a cleaved fiber while it is still in the cleaver. In this manner, the cleaved end faces may be checked more quickly.